In the quest to improve hydrocarbon recovery and reduce the developmental cost in challenging, multi-stacked compartmentalized fields as well as oil-rim reservoirs (reservoirs wedged between a gas-cap and an aquifer), well type and completion design has been found to play a significant role. Multi-stacked, compartmentalized, and/or oil rim reservoirs may be complex in structure with relatively high levels of reservoir heterogeneity. By their nature, these reservoirs may present many challenges for active reservoir management if they are to be productive and commercially viable.
Several technologies are known for developing such fields. One technique is the use of dual-string or multi-string completions, in which a separate production string is positioned within the well for serving each discrete production zone. That is, multiple strings may be positioned side-by-side within the main, or parent, wellbore. However, cross-sectional area in a wellbore is a limited commodity, and the main wellbore must accommodate equipment and multiple tubing strings having sufficient flow area. Although for shallow wells that only intercept two zones, dual-completions may be commercially viable, such a system may be less than ideal for wells with greater than two zones or for deep or complex wells with long horizontal runs.
Another technique is to use a single production string to serve all of the production zones and to employ selective flow control downhole for each zone. Such systems are commonly referred to as “intelligent well completions” and may include multi-lateral, selective and controlled injection and depletion systems, dynamic active-flow-control valves, and downhole pressure, temperature, and/or composition monitoring systems. Intelligent completions may prevent or delay water or gas breakthrough, increase the productivity index, and also, properly control drawdown to mitigate wellbore instability, sand failure, and conformance issues. Active flow-control valves may allow for fewer wells to be drilled by enabling efficient commingled injection and production wells to be developed. Moreover, with downhole monitoring and surveillance, work-overs can be minimized, further reducing operating costs. Accordingly, intelligent well completions have become a technology of interest for optimizing the productivity and ultimate recovery of hydrocarbons.